An experimental investigation of the Buneman instability

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Date

1981-04

Author

Paulson, James Daniel

Type

Thesis

Degree Level

Masters

Abstract

The Plasma Betatron, a toroidal turbulent heating device, is
modified so that a short (200 nsec duration) electric field pulse
(maximum strength 650 V/m) is applied to accelerate electrons to a
drift velocity vD
much larger than the initial thermal velocity VTH.
The device has a major radius of 19 cm and a minor radius of 3 cm, and
a plasma having an electron density of 4 x 1016 ~ 1.2 x 1017 m-3 is
prepared by rf ionization in a toroidal magnetic field of ~.2 T. A
ratio of VD/VTH ~> 5 has been realized which is sufficient for the
development of the electron-ion two stream instability. Rapid decay
of the plasma current, concurrent turbulent electron heating and an
anomalously high electron-ion collision frequency are also observed.
However, the Buneman frequency is not observed. Following the
collapse of the current, strong oscillations near the ion plasma
frequency are detected. Most of the experimental results are in
qualitative agreement with recent theoretical predictions.